diff --git a/src/v2/bigtable_client.js b/src/v2/bigtable_client.js
index cc3d80e02..8f560acc4 100644
--- a/src/v2/bigtable_client.js
+++ b/src/v2/bigtable_client.js
@@ -71,13 +71,13 @@ class BigtableClient {
     // Create a `gaxGrpc` object, with any grpc-specific options
     // sent to the client.
     opts.scopes = this.constructor.scopes;
-    var gaxGrpc = new gax.GrpcClient(opts);
+    const gaxGrpc = new gax.GrpcClient(opts);
 
     // Save the auth object to the client, for use by other methods.
     this.auth = gaxGrpc.auth;
 
     // Determine the client header string.
-    var clientHeader = [
+    const clientHeader = [
       `gl-node/${process.version}`,
       `grpc/${gaxGrpc.grpcVersion}`,
       `gax/${gax.version}`,
@@ -88,7 +88,7 @@ class BigtableClient {
     }
 
     // Load the applicable protos.
-    var protos = merge(
+    const protos = merge(
       {},
       gaxGrpc.loadProto(
         path.join(__dirname, '..', '..', 'protos'),
@@ -114,7 +114,7 @@ class BigtableClient {
     };
 
     // Put together the default options sent with requests.
-    var defaults = gaxGrpc.constructSettings(
+    const defaults = gaxGrpc.constructSettings(
       'google.bigtable.v2.Bigtable',
       gapicConfig,
       opts.clientConfig,
@@ -128,14 +128,14 @@ class BigtableClient {
 
     // Put together the "service stub" for
     // google.bigtable.v2.Bigtable.
-    var bigtableStub = gaxGrpc.createStub(
+    const bigtableStub = gaxGrpc.createStub(
       protos.google.bigtable.v2.Bigtable,
       opts
     );
 
     // Iterate over each of the methods that the service provides
     // and create an API call method for each.
-    var bigtableStubMethods = [
+    const bigtableStubMethods = [
       'readRows',
       'sampleRowKeys',
       'mutateRow',
@@ -148,7 +148,7 @@ class BigtableClient {
         bigtableStub.then(
           stub =>
             function() {
-              var args = Array.prototype.slice.call(arguments, 0);
+              const args = Array.prototype.slice.call(arguments, 0);
               return stub[methodName].apply(stub, args);
             }
         ),
@@ -238,11 +238,11 @@ class BigtableClient {
    *
    * const bigtable = require('@google-cloud/bigtable');
    *
-   * var client = new bigtable.v2.BigtableClient({
+   * const client = new bigtable.v2.BigtableClient({
    *   // optional auth parameters.
    * });
    *
-   * var formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
+   * const formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
    * client.readRows({tableName: formattedTableName}).on('data', response => {
    *   // doThingsWith(response)
    * });
@@ -285,11 +285,11 @@ class BigtableClient {
    *
    * const bigtable = require('@google-cloud/bigtable');
    *
-   * var client = new bigtable.v2.BigtableClient({
+   * const client = new bigtable.v2.BigtableClient({
    *   // optional auth parameters.
    * });
    *
-   * var formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
+   * const formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
    * client.sampleRowKeys({tableName: formattedTableName}).on('data', response => {
    *   // doThingsWith(response)
    * });
@@ -343,21 +343,21 @@ class BigtableClient {
    *
    * const bigtable = require('@google-cloud/bigtable');
    *
-   * var client = new bigtable.v2.BigtableClient({
+   * const client = new bigtable.v2.BigtableClient({
    *   // optional auth parameters.
    * });
    *
-   * var formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
-   * var rowKey = '';
-   * var mutations = [];
-   * var request = {
+   * const formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
+   * const rowKey = '';
+   * const mutations = [];
+   * const request = {
    *   tableName: formattedTableName,
    *   rowKey: rowKey,
    *   mutations: mutations,
    * };
    * client.mutateRow(request)
    *   .then(responses => {
-   *     var response = responses[0];
+   *     const response = responses[0];
    *     // doThingsWith(response)
    *   })
    *   .catch(err => {
@@ -411,13 +411,13 @@ class BigtableClient {
    *
    * const bigtable = require('@google-cloud/bigtable');
    *
-   * var client = new bigtable.v2.BigtableClient({
+   * const client = new bigtable.v2.BigtableClient({
    *   // optional auth parameters.
    * });
    *
-   * var formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
-   * var entries = [];
-   * var request = {
+   * const formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
+   * const entries = [];
+   * const request = {
    *   tableName: formattedTableName,
    *   entries: entries,
    * };
@@ -491,19 +491,19 @@ class BigtableClient {
    *
    * const bigtable = require('@google-cloud/bigtable');
    *
-   * var client = new bigtable.v2.BigtableClient({
+   * const client = new bigtable.v2.BigtableClient({
    *   // optional auth parameters.
    * });
    *
-   * var formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
-   * var rowKey = '';
-   * var request = {
+   * const formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
+   * const rowKey = '';
+   * const request = {
    *   tableName: formattedTableName,
    *   rowKey: rowKey,
    * };
    * client.checkAndMutateRow(request)
    *   .then(responses => {
-   *     var response = responses[0];
+   *     const response = responses[0];
    *     // doThingsWith(response)
    *   })
    *   .catch(err => {
@@ -567,21 +567,21 @@ class BigtableClient {
    *
    * const bigtable = require('@google-cloud/bigtable');
    *
-   * var client = new bigtable.v2.BigtableClient({
+   * const client = new bigtable.v2.BigtableClient({
    *   // optional auth parameters.
    * });
    *
-   * var formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
-   * var rowKey = '';
-   * var rules = [];
-   * var request = {
+   * const formattedTableName = client.tablePath('[PROJECT]', '[INSTANCE]', '[TABLE]');
+   * const rowKey = '';
+   * const rules = [];
+   * const request = {
    *   tableName: formattedTableName,
    *   rowKey: rowKey,
    *   rules: rules,
    * };
    * client.readModifyWriteRow(request)
    *   .then(responses => {
-   *     var response = responses[0];
+   *     const response = responses[0];
    *     // doThingsWith(response)
    *   })
    *   .catch(err => {
diff --git a/src/v2/doc/google/bigtable/v2/doc_bigtable.js b/src/v2/doc/google/bigtable/v2/doc_bigtable.js
index 9f4e13f71..dc26a680e 100644
--- a/src/v2/doc/google/bigtable/v2/doc_bigtable.js
+++ b/src/v2/doc/google/bigtable/v2/doc_bigtable.js
@@ -46,7 +46,7 @@
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ReadRowsRequest definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var ReadRowsRequest = {
+const ReadRowsRequest = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -69,7 +69,7 @@ var ReadRowsRequest = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ReadRowsResponse definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var ReadRowsResponse = {
+const ReadRowsResponse = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 
   /**
@@ -162,7 +162,7 @@ var ReadRowsResponse = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.SampleRowKeysRequest definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var SampleRowKeysRequest = {
+const SampleRowKeysRequest = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -188,7 +188,7 @@ var SampleRowKeysRequest = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.SampleRowKeysResponse definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var SampleRowKeysResponse = {
+const SampleRowKeysResponse = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -218,7 +218,7 @@ var SampleRowKeysResponse = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.MutateRowRequest definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var MutateRowRequest = {
+const MutateRowRequest = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -228,7 +228,7 @@ var MutateRowRequest = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.MutateRowResponse definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var MutateRowResponse = {
+const MutateRowResponse = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -255,7 +255,7 @@ var MutateRowResponse = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.MutateRowsRequest definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var MutateRowsRequest = {
+const MutateRowsRequest = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 
   /**
@@ -291,7 +291,7 @@ var MutateRowsRequest = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.MutateRowsResponse definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var MutateRowsResponse = {
+const MutateRowsResponse = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 
   /**
@@ -362,7 +362,7 @@ var MutateRowsResponse = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.CheckAndMutateRowRequest definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var CheckAndMutateRowRequest = {
+const CheckAndMutateRowRequest = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -377,7 +377,7 @@ var CheckAndMutateRowRequest = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.CheckAndMutateRowResponse definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var CheckAndMutateRowResponse = {
+const CheckAndMutateRowResponse = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -408,7 +408,7 @@ var CheckAndMutateRowResponse = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ReadModifyWriteRowRequest definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var ReadModifyWriteRowRequest = {
+const ReadModifyWriteRowRequest = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -424,6 +424,6 @@ var ReadModifyWriteRowRequest = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ReadModifyWriteRowResponse definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/bigtable.proto}
  */
-var ReadModifyWriteRowResponse = {
+const ReadModifyWriteRowResponse = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
\ No newline at end of file
diff --git a/src/v2/doc/google/bigtable/v2/doc_data.js b/src/v2/doc/google/bigtable/v2/doc_data.js
index 66f5c4a35..d8244bf5d 100644
--- a/src/v2/doc/google/bigtable/v2/doc_data.js
+++ b/src/v2/doc/google/bigtable/v2/doc_data.js
@@ -34,7 +34,7 @@
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.Row definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var Row = {
+const Row = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -59,7 +59,7 @@ var Row = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.Family definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var Family = {
+const Family = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -83,7 +83,7 @@ var Family = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.Column definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var Column = {
+const Column = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -110,7 +110,7 @@ var Column = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.Cell definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var Cell = {
+const Cell = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -133,7 +133,7 @@ var Cell = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.RowRange definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var RowRange = {
+const RowRange = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -152,7 +152,7 @@ var RowRange = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.RowSet definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var RowSet = {
+const RowSet = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -181,7 +181,7 @@ var RowSet = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ColumnRange definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var ColumnRange = {
+const ColumnRange = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -198,7 +198,7 @@ var ColumnRange = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.TimestampRange definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var TimestampRange = {
+const TimestampRange = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -221,7 +221,7 @@ var TimestampRange = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ValueRange definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var ValueRange = {
+const ValueRange = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -438,7 +438,7 @@ var ValueRange = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.RowFilter definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var RowFilter = {
+const RowFilter = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 
   /**
@@ -564,7 +564,7 @@ var RowFilter = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.Mutation definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var Mutation = {
+const Mutation = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 
   /**
@@ -675,6 +675,6 @@ var Mutation = {
  * @memberof google.bigtable.v2
  * @see [google.bigtable.v2.ReadModifyWriteRule definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/bigtable/v2/data.proto}
  */
-var ReadModifyWriteRule = {
+const ReadModifyWriteRule = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
\ No newline at end of file
diff --git a/src/v2/doc/google/protobuf/doc_any.js b/src/v2/doc/google/protobuf/doc_any.js
index c5c5bbafa..3accb1fc0 100644
--- a/src/v2/doc/google/protobuf/doc_any.js
+++ b/src/v2/doc/google/protobuf/doc_any.js
@@ -131,6 +131,6 @@
  * @memberof google.protobuf
  * @see [google.protobuf.Any definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/any.proto}
  */
-var Any = {
+const Any = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
\ No newline at end of file
diff --git a/src/v2/doc/google/protobuf/doc_wrappers.js b/src/v2/doc/google/protobuf/doc_wrappers.js
index 791b600ab..363b6391a 100644
--- a/src/v2/doc/google/protobuf/doc_wrappers.js
+++ b/src/v2/doc/google/protobuf/doc_wrappers.js
@@ -27,7 +27,7 @@
  * @memberof google.protobuf
  * @see [google.protobuf.DoubleValue definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var DoubleValue = {
+const DoubleValue = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -43,7 +43,7 @@ var DoubleValue = {
  * @memberof google.protobuf
  * @see [google.protobuf.FloatValue definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var FloatValue = {
+const FloatValue = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -59,7 +59,7 @@ var FloatValue = {
  * @memberof google.protobuf
  * @see [google.protobuf.Int64Value definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var Int64Value = {
+const Int64Value = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -75,7 +75,7 @@ var Int64Value = {
  * @memberof google.protobuf
  * @see [google.protobuf.UInt64Value definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var UInt64Value = {
+const UInt64Value = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -91,7 +91,7 @@ var UInt64Value = {
  * @memberof google.protobuf
  * @see [google.protobuf.Int32Value definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var Int32Value = {
+const Int32Value = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -107,7 +107,7 @@ var Int32Value = {
  * @memberof google.protobuf
  * @see [google.protobuf.UInt32Value definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var UInt32Value = {
+const UInt32Value = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -123,7 +123,7 @@ var UInt32Value = {
  * @memberof google.protobuf
  * @see [google.protobuf.BoolValue definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var BoolValue = {
+const BoolValue = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -139,7 +139,7 @@ var BoolValue = {
  * @memberof google.protobuf
  * @see [google.protobuf.StringValue definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var StringValue = {
+const StringValue = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
 
@@ -155,6 +155,6 @@ var StringValue = {
  * @memberof google.protobuf
  * @see [google.protobuf.BytesValue definition in proto format]{@link https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto}
  */
-var BytesValue = {
+const BytesValue = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
\ No newline at end of file
diff --git a/src/v2/doc/google/rpc/doc_status.js b/src/v2/doc/google/rpc/doc_status.js
index 7122f1682..13cfcab10 100644
--- a/src/v2/doc/google/rpc/doc_status.js
+++ b/src/v2/doc/google/rpc/doc_status.js
@@ -87,6 +87,6 @@
  * @memberof google.rpc
  * @see [google.rpc.Status definition in proto format]{@link https://github.com/googleapis/googleapis/blob/master/google/rpc/status.proto}
  */
-var Status = {
+const Status = {
   // This is for documentation. Actual contents will be loaded by gRPC.
 };
\ No newline at end of file
diff --git a/test/gapic-v2.js b/test/gapic-v2.js
index cab1dbbd7..4046c87dd 100644
--- a/test/gapic-v2.js
+++ b/test/gapic-v2.js
@@ -19,31 +19,31 @@ const through2 = require('through2');
 
 const bigtableModule = require('../src');
 
-var FAKE_STATUS_CODE = 1;
-var error = new Error();
+const FAKE_STATUS_CODE = 1;
+const error = new Error();
 error.code = FAKE_STATUS_CODE;
 
 describe('BigtableClient', () => {
   describe('readRows', () => {
     it('invokes readRows without error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var request = {
+      const request = {
         tableName: formattedTableName,
       };
 
       // Mock response
-      var lastScannedRowKey = '-126';
-      var expectedResponse = {
+      const lastScannedRowKey = '-126';
+      const expectedResponse = {
         lastScannedRowKey: lastScannedRowKey,
       };
 
@@ -53,7 +53,7 @@ describe('BigtableClient', () => {
         expectedResponse
       );
 
-      var stream = client.readRows(request);
+      const stream = client.readRows(request);
       stream.on('data', response => {
         assert.deepStrictEqual(response, expectedResponse);
         done();
@@ -66,18 +66,18 @@ describe('BigtableClient', () => {
     });
 
     it('invokes readRows with error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var request = {
+      const request = {
         tableName: formattedTableName,
       };
 
@@ -88,7 +88,7 @@ describe('BigtableClient', () => {
         error
       );
 
-      var stream = client.readRows(request);
+      const stream = client.readRows(request);
       stream.on('data', () => {
         assert.fail();
       });
@@ -104,25 +104,25 @@ describe('BigtableClient', () => {
 
   describe('sampleRowKeys', () => {
     it('invokes sampleRowKeys without error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var request = {
+      const request = {
         tableName: formattedTableName,
       };
 
       // Mock response
-      var rowKey = '122';
-      var offsetBytes = 889884095;
-      var expectedResponse = {
+      const rowKey = '122';
+      const offsetBytes = 889884095;
+      const expectedResponse = {
         rowKey: rowKey,
         offsetBytes: offsetBytes,
       };
@@ -133,7 +133,7 @@ describe('BigtableClient', () => {
         expectedResponse
       );
 
-      var stream = client.sampleRowKeys(request);
+      const stream = client.sampleRowKeys(request);
       stream.on('data', response => {
         assert.deepStrictEqual(response, expectedResponse);
         done();
@@ -146,18 +146,18 @@ describe('BigtableClient', () => {
     });
 
     it('invokes sampleRowKeys with error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var request = {
+      const request = {
         tableName: formattedTableName,
       };
 
@@ -168,7 +168,7 @@ describe('BigtableClient', () => {
         error
       );
 
-      var stream = client.sampleRowKeys(request);
+      const stream = client.sampleRowKeys(request);
       stream.on('data', () => {
         assert.fail();
       });
@@ -184,27 +184,27 @@ describe('BigtableClient', () => {
 
   describe('mutateRow', () => {
     it('invokes mutateRow without error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var rowKey = '122';
-      var mutations = [];
-      var request = {
+      const rowKey = '122';
+      const mutations = [];
+      const request = {
         tableName: formattedTableName,
         rowKey: rowKey,
         mutations: mutations,
       };
 
       // Mock response
-      var expectedResponse = {};
+      const expectedResponse = {};
 
       // Mock Grpc layer
       client._innerApiCalls.mutateRow = mockSimpleGrpcMethod(
@@ -220,20 +220,20 @@ describe('BigtableClient', () => {
     });
 
     it('invokes mutateRow with error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var rowKey = '122';
-      var mutations = [];
-      var request = {
+      const rowKey = '122';
+      const mutations = [];
+      const request = {
         tableName: formattedTableName,
         rowKey: rowKey,
         mutations: mutations,
@@ -257,25 +257,25 @@ describe('BigtableClient', () => {
 
   describe('mutateRows', () => {
     it('invokes mutateRows without error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var entries = [];
-      var request = {
+      const entries = [];
+      const request = {
         tableName: formattedTableName,
         entries: entries,
       };
 
       // Mock response
-      var expectedResponse = {};
+      const expectedResponse = {};
 
       // Mock Grpc layer
       client._innerApiCalls.mutateRows = mockServerStreamingGrpcMethod(
@@ -283,7 +283,7 @@ describe('BigtableClient', () => {
         expectedResponse
       );
 
-      var stream = client.mutateRows(request);
+      const stream = client.mutateRows(request);
       stream.on('data', response => {
         assert.deepStrictEqual(response, expectedResponse);
         done();
@@ -296,19 +296,19 @@ describe('BigtableClient', () => {
     });
 
     it('invokes mutateRows with error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var entries = [];
-      var request = {
+      const entries = [];
+      const request = {
         tableName: formattedTableName,
         entries: entries,
       };
@@ -320,7 +320,7 @@ describe('BigtableClient', () => {
         error
       );
 
-      var stream = client.mutateRows(request);
+      const stream = client.mutateRows(request);
       stream.on('data', () => {
         assert.fail();
       });
@@ -336,26 +336,26 @@ describe('BigtableClient', () => {
 
   describe('checkAndMutateRow', () => {
     it('invokes checkAndMutateRow without error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var rowKey = '122';
-      var request = {
+      const rowKey = '122';
+      const request = {
         tableName: formattedTableName,
         rowKey: rowKey,
       };
 
       // Mock response
-      var predicateMatched = true;
-      var expectedResponse = {
+      const predicateMatched = true;
+      const expectedResponse = {
         predicateMatched: predicateMatched,
       };
 
@@ -373,19 +373,19 @@ describe('BigtableClient', () => {
     });
 
     it('invokes checkAndMutateRow with error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var rowKey = '122';
-      var request = {
+      const rowKey = '122';
+      const request = {
         tableName: formattedTableName,
         rowKey: rowKey,
       };
@@ -408,27 +408,27 @@ describe('BigtableClient', () => {
 
   describe('readModifyWriteRow', () => {
     it('invokes readModifyWriteRow without error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var rowKey = '122';
-      var rules = [];
-      var request = {
+      const rowKey = '122';
+      const rules = [];
+      const request = {
         tableName: formattedTableName,
         rowKey: rowKey,
         rules: rules,
       };
 
       // Mock response
-      var expectedResponse = {};
+      const expectedResponse = {};
 
       // Mock Grpc layer
       client._innerApiCalls.readModifyWriteRow = mockSimpleGrpcMethod(
@@ -444,20 +444,20 @@ describe('BigtableClient', () => {
     });
 
     it('invokes readModifyWriteRow with error', done => {
-      var client = new bigtableModule.v2.BigtableClient({
+      const client = new bigtableModule.v2.BigtableClient({
         credentials: {client_email: 'bogus', private_key: 'bogus'},
         projectId: 'bogus',
       });
 
       // Mock request
-      var formattedTableName = client.tablePath(
+      const formattedTableName = client.tablePath(
         '[PROJECT]',
         '[INSTANCE]',
         '[TABLE]'
       );
-      var rowKey = '122';
-      var rules = [];
-      var request = {
+      const rowKey = '122';
+      const rules = [];
+      const request = {
         tableName: formattedTableName,
         rowKey: rowKey,
         rules: rules,
@@ -496,7 +496,7 @@ function mockSimpleGrpcMethod(expectedRequest, response, error) {
 function mockServerStreamingGrpcMethod(expectedRequest, response, error) {
   return actualRequest => {
     assert.deepStrictEqual(actualRequest, expectedRequest);
-    var mockStream = through2.obj((chunk, enc, callback) => {
+    const mockStream = through2.obj((chunk, enc, callback) => {
       if (error) {
         callback(error);
       } else {